Package explorer view of Flash Builder crashes

I cannot use the package explorer of Flash Builder, it shows an error instead, and the projects won't load. Please assist, Claudius.

Error log excerpt:

!SESSION 2017-01-22 17:51:37.098 -----------------------------------------------

eclipse.buildId=M20110909-1335

java.version=1.6.0_31

java.vendor=Sun Microsystems Inc.

BootLoader constants: OS=win32, ARCH=x86_64, WS=win32, NL=en_US

Command-line arguments: -os win32 -ws win32 -arch x86_64

!ENTRY org.eclipse.osgi 4 0 2017-01-22 17:51:48.316

!MESSAGE An error occurred while automatically activating bundle com.adobe.flexbuilder.exportimport (47).

!STACK 0

org.osgi.framework.BundleException: Exception in com.adobe.flexbuilder.exportimport.ExportImportPlugin.start() of bundle com.adobe.flexbuilder.exportimport.

at org.eclipse.osgi.framework.internal.core.BundleContextImpl.startActivator(BundleContextIm pl.java:734)

at org.eclipse.osgi.framework.internal.core.BundleContextImpl.start(BundleContextImpl.java:6 83)

at org.eclipse.osgi.framework.internal.core.BundleHost.startWorker(BundleHost.java:381)

at org.eclipse.osgi.framework.internal.core.AbstractBundle.start(AbstractBundle.java:299)

at org.eclipse.osgi.framework.util.SecureAction.start(SecureAction.java:440)

at org.eclipse.osgi.internal.loader.BundleLoader.setLazyTrigger(BundleLoader.java:268)

at org.eclipse.core.runtime.internal.adaptor.EclipseLazyStarter.postFindLocalClass(EclipseLa zyStarter.java:107)

at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.findLocalClass(ClasspathManager.java :462)

at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.findLocalClass(DefaultClassLoade r.java:216)

at org.eclipse.osgi.internal.loader.BundleLoader.findLocalClass(BundleLoader.java:400)

at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:476)

at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:429)

at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:417)

at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.jav a:107)

at java.lang.ClassLoader.loadClass(Unknown Source)

at org.eclipse.osgi.internal.loader.BundleLoader.loadClass(BundleLoader.java:345)

at org.eclipse.osgi.framework.internal.core.BundleHost.loadClass(BundleHost.java:229)

at org.eclipse.osgi.framework.internal.core.AbstractBundle.loadClass(AbstractBundle.java:120 7)

at org.eclipse.core.internal.registry.osgi.RegistryStrategyOSGI.createExecutableExtension(Re gistryStrategyOSGI.java:174)

at org.eclipse.core.internal.registry.ExtensionRegistry.createExecutableExtension(ExtensionR egistry.java:905)

at org.eclipse.core.internal.registry.ConfigurationElement.createExecutableExtension(Configu rationElement.java:243)

at org.eclipse.core.internal.registry.ConfigurationElementHandle.createExecutableExtension(C onfigurationElementHandle.java:55)

at org.eclipse.ui.internal.WorkbenchPlugin$1.run(WorkbenchPlugin.java:268)

at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:52)

at org.eclipse.ui.internal.WorkbenchPlugin.createExtension(WorkbenchPlugin.java:264)

at org.eclipse.ui.internal.EarlyStartupRunnable.getExecutableExtension(EarlyStartupRunnable. java:117)

at org.eclipse.ui.internal.EarlyStartupRunnable.run(EarlyStartupRunnable.java:66)

at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)

at org.eclipse.ui.internal.Workbench$63.run(Workbench.java:2465)

at org.eclipse.core.internal.jobs.Worker.run(Worker.java:54)

Caused by: java.lang.NoClassDefFoundError: com/adobe/flash/compiler/definitions/IDefinition

at com.adobe.flexbuilder.exportimport.ExportImportPlugin.start(ExportImportPlugin.java:70)

at org.eclipse.osgi.framework.internal.core.BundleContextImpl$1.run(BundleContextImpl.java:7 11)

at java.security.AccessController.doPrivileged(Native Method)

at org.eclipse.osgi.framework.internal.core.BundleContextImpl.startActivator(BundleContextIm pl.java:702)

... 29 more

Caused by: java.lang.ClassNotFoundException: com.adobe.flash.compiler.definitions.IDefinition

at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:513)

at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:429)

at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:417)

at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.jav a:107)

at java.lang.ClassLoader.loadClass(Unknown Source)

... 33 more

Root exception:

java.lang.NoClassDefFoundError: com/adobe/flash/compiler/definitions/IDefinition